(1) Field of the Invention
The present invention relates to a method for joining a separating adhesive tape to a protective tape joined to a front face (a face on which a pattern is formed) of a semiconductor wafer (hereinafter, simply referred to as “wafer”), a method for separating the protective tape from the front face of the wafer by means of the separating adhesive tape, and apparatuses using the methods.
(2) Description of the Related Art
After completion of a pattern forming process, a semiconductor wafer is subjected to a back grinding process in a state that a protective tape is joined to a front face of the semiconductor wafer in order to protect a pattern. Thereafter, the protective tape is separated from the front face of the wafer, and then the wafer is subjected to a dicing process in which the wafer is divided into chips.
JP-A 2002-124494 discloses one example of a technique for separating a protective tape from a front face of a wafer. According to this technique, a wafer is held by a table in a state that a front face, to which a protective tape is joined, of the wafer is directed upward. Then, a separating adhesive tape is joined to the protective tape while being separated in a reverse direction. Thus, the protective tape joined to and integrated with the adhesive tape is separated from the front face of the wafer.
Recently, a wafer is made thinner in response to needs for size reduction and high-density package as to an electronic device. However, a wafer made thin so as to have a thickness of several tens of micrometers becomes cracked or chipped readily due to occurrence of warpage. Consequently, there is a high possibility that such wafer is damaged in various processing steps and handling. In order to avoid such disadvantage, there is the following proposition. That is, a center of a wafer is ground in a back grinding process to form an annular convex portion at an outer periphery of a back face of the wafer; thus, the wafer is allowed to have rigidity. That is, the wafer is processed so as to be less susceptible to damage in handling.
The annular convex portion left on the wafer brings rigidity capable of withstanding warpage. Therefore, such wafer facilitates handling without being damaged. If the wafer is held by the table in a state that a back face thereof is directed downward, however, the annular convex portion comes into contact with the table, but a flat concave portion corresponding to the center of the back face of the wafer does not come into contact with the table. Consequently, there is a problem that it is impossible to join a separating adhesive tape to a wafer, which has been made thin, with good accuracy and to separate the separating adhesive tape together with a protective tape from the wafer with good accuracy.